One of the functions of switching system network management is to provide the capability of central alarm monitoring for all of the switching exchanges connected in the network. Ideally this would provide real time or near real time notification of alarm conditions occurring in each switching system to a central monitoring station. It should also provide accurate indication of what the alarm is, and not to consume excessive trunking resources.
Central alarm monitoring has generally been solved in one of four ways.
Using a packet switching backbone network, the nodes (switching machines) of the network are interconnected thereby to a central alarm monitoring system. When an alarm transition is detected by a network node, the node sends an information packet addressed to the central monitoring system via the backbone. The packet switching backbone assures that the information packet reaches its desired destination.
However this approach is expensive for those networks which are not already equipped with packet switching capability, e.g. circuit switched networks which only handle voice traffic or circuit switched data calls.
A second system uses polling without dedicated circuit switched links. In this case, a central monitoring system continuously polls each node in the network to collect alarm status information. The current information is compared against the previous, and if not equivalent, the monitoring system considers that an alarm transition has occurred. After collecting information from one or from N nodes, (N nodes may be polled simultaneously, depending on the configuration of the polling system), the next one or N nodes is polled. When N equals the number of nodes in the network, the third type of system described below exists.
This approach has two major deficiencies. In order to meet the requirement of real time or near real time performance, polling must occur frequently. It utilizes valuable trunk circuitry each time polling occurs. Also, depending on the number of network nodes being monitored and the number of nodes that can be polled simultaneously, this solution may not be able to provide real time or near real time performance requirements.
A third approach uses polling with "nailed-up" (dedicated) circuit switched links. In this approach, the central monitoring system has a dedicated circuit switch connection to each node in the network. Periodically, current alarm information is compared against the previous and, if not equivalent, the monitoring system considers that an alarm transition has occurred.
This approach monopolizes valuable trunk circuitry without properly utilizing the bandwidth. Depending on the number of nodes being monitored, the cost of the trunk circuitry may be prohibitive.
In a fourth approach, there is automatic dial-back occurring with switch contact closures. In this approach, the network nodes are hard-wired to additional hardware. When certain hard-wired conditions occur, the attached hardware dials a remote location to report the hard-wired condition.
This approach has two major deficiencies. It requires additional hardware in the network, thereby increasing cost of the solution and the number of hardware components that might fail. It also does not provide adequate resolution for alarm conditions which can occur within a complex network node since it is not an integrated solution. For instance, it may be able to detect and signal that the node has experienced a power outage, but would not be able to detect and signal that e.g. 20% of the trunking resource has been taken out of service, unless this condition was associated with a contact closure, which would be unlikely.